In recent years, photoreceptors which include organic photoconductive materials, particularly phthalocyanine type photoconductive materials, have been proposed. Such photoreceptors do not cause sanitary problems, as do photoreceptors which contain selenium, cadmium sulfide, etc., and they are highly sensitive towards rays of long wavelength such as are produced by semiconductor lasers. But photoreceptors containing a phthalocyanine photoconductive powder dispersed in a binder resin have many traps so that they show the so-called induction effect, which is a phenomenon in which there is a time lag between exposure to rays and attenuation of electric potential.
In order to reduce this induction effect and thus improve the sensitivity of the photoreceptors, it is known to incorporate a charge-transfer agent in the photosensitive layer, particularly various kinds of hydrazone compounds. For example, Japanese Patent Application Kokai (Laid-open) No. 150128/1979 discloses photoreceptors for electrophotography containing hydrazone compounds having a heterocyclic ring. Japanese Patent Application Kokai No. 42380/1980 gives many examples of hydrazone compounds represented by a general formula. Japanese Patent Application Kokai No. 46760/1980 discloses the application of hydrazone compounds having a carbazole ring to photoreceptors for electrophotography. Japanese Patent Application Kokai No. 52063/1980 discloses hydrazone compounds having a condensed polycyclic or heterocyclic group. Further, Japanese Patent Application Kokai No. 52064/1980 discloses a technique which uses hydrazone compounds having a dibenzylaminophenyl group as a charge-carrying substance for electrophotography, but this phenyl group has no substituent other than a dibenzylamino group.
Photoreceptors that include the hydrazone compound disclosed in the noted citations are not satisfactory in their sensitivity, their repeat stability, their residual voltage (V.sub.R) and/or their electric potential (Vi.sub.R) at a maximum exposure.